Drilled Extreme Events from the Past: Unravelling a long-term history of giant earthquakes and tsunamis for geohazards assessment

The study of giant earthquakes and tsunamis is essential in modern hazards assessment.

However, these natural disasters have a long recurrence time, and instrumental as historical records are inadequate to reduce uncertainties in hazards predictions.

Submarine paleoseismology is a novel approach that combines sedimentology and marine geology to identify, describe and date earthquake deposits. Its strength relies on covering much longer periods than instrumental or historical catalogues.

Recent technological advances have allowed to correlate homogenite-turbidite deposits (HmTu) with seismic and tsunami events.

Along the Japan Trench, the oceanographic cruise IODP 386 drilled and cored the deepest HmTu records in the scientific ocean drilling history.DEEP will use these unique seismic and tsunami sediment archives to 1)estimate their long-term recurrence time, 2) reduce epistemic uncertainties in hazards assessment and 3) provide the most complete on-and-offshore catalogue of giant events over several thousands of years.

I will develop tools to unravel prehistorical events using an innovative multiproxy approach using micro-X-ray computed tomography (XCT) images, physical and geochemical properties along with marine geophysical datasets and chronostratigraphic correlations.

Integration with onshore records will produce the first database of its kind for Japan and other high-risk areas worldwide, improving knowledge on seismic cycles and reducing the data uncertainties used by scientists and decision-makers.

The governments need these crucial tools to take the necessary measures to protect their population and infrastructures.

DEEP will result in a clear three-way-transfer of complementary skills in between myself (deep-marine sedimentary processes), the host institution (geological hazards assessment) and the partner institution (submarine paleoseismology). I will develop new skills in micro-XCT, computational merging, earthquake modelling and geohazards assessment.